...like a chip in the key.? And is it worth buying a aftermarket version as the car has no alarm fitted.
many thanks.

Yes, your car is equipped with an immobilizer in the key (called "EWS-II").

Chances are, you will probably only need to worry about the smash-and-grab kind of thieves. Joyriders will probably target hot hatches that are easier to steal.

Whatever alarm system you choose, as long as it's Thatcham Category 1 approved, and has a very noticeable & big flashing red LED in the console, you should be fine.

And of course follow common sense, don't leave anything that would attract break-ins in plain view in your car. Keep everything out of sight when you park your car.